diff --git a/types/index.d.ts b/types/index.d.ts
index b9bfc273..6fe99b61 100644
--- a/types/index.d.ts
+++ b/types/index.d.ts
@@ -37,8 +37,8 @@ export type DetailsObject = {
 }
 
 export type ExtendedMastery = {
-  modifier: number
-  strength: number
+  modifier?: number
+  strength?: number
 }
 
 export type CharacterOverMastery = {